Add a fast-path for independent inherited properties

third_party/WebKit/Source/core/style/ComputedStyle.cpp

Index: third_party/WebKit/Source/core/style/ComputedStyle.cpp
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.cpp b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
index 3a671d051c066787e9e0174febf1e9470cb43c82..d4ecea553149fae5db25b9120f62e06e9f4021a2 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.cpp
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
@@ -65,6 +65,8 @@ struct SameSizeAsBorderValue {
 
 static_assert(sizeof(BorderValue) == sizeof(SameSizeAsBorderValue), "BorderValue should stay small");
 
+// Since different compilers/architectures pack ComputedStyle differently,
+// re-create the same structure for an accurate size comparison.
 struct SameSizeAsComputedStyle : public RefCounted<SameSizeAsComputedStyle> {
     void* dataRefs[7];
     void* ownPtrs[1];
@@ -197,8 +199,15 @@ StyleRecalcChange ComputedStyle::stylePropagationDiff(const ComputedStyle* oldSt
         || oldStyle->hasTextCombine() != newStyle->hasTextCombine())
         return Reattach;
 
-    if (!oldStyle->inheritedEqual(*newStyle)
-        || !oldStyle->loadingCustomFontsEqual(*newStyle)
+    bool independentEqual = oldStyle->independentInheritedEqual(*newStyle);
+    bool nonIndependentEqual = oldStyle->nonIndependentInheritedEqual(*newStyle);
+    if (!independentEqual || !nonIndependentEqual) {
+        if (nonIndependentEqual && !oldStyle->hasExplicitlyInheritedProperties())
+            return IndependentInherit;
+        return Inherit;
+    }
+
+    if (!oldStyle->loadingCustomFontsEqual(*newStyle)
         || oldStyle->alignItems() != newStyle->alignItems()
         || oldStyle->justifyItems() != newStyle->justifyItems())
         return Inherit;
@@ -212,6 +221,15 @@ StyleRecalcChange ComputedStyle::stylePropagationDiff(const ComputedStyle* oldSt
     return NoInherit;
 }
 
+// TODO(sashab): Generate this function.
+void ComputedStyle::propagateIndependentInheritedProperties(const ComputedStyle& parentStyle)
+{
+    if (m_nonInheritedData.m_isPointerEventsInherited)
+        setPointerEvents(parentStyle.pointerEvents());
+    if (m_nonInheritedData.m_isVisibilityInherited)
+        setVisibility(parentStyle.visibility());
+}
+
 StyleSelfAlignmentData resolvedSelfAlignment(const StyleSelfAlignmentData& value, ItemPosition normalValueBehavior)
 {
     // To avoid needing to copy the RareNonInheritedData, we repurpose the 'auto' flag to not just mean 'auto' prior to running the StyleAdjuster but also mean 'normal' after running it.
@@ -362,6 +380,11 @@ void ComputedStyle::copyNonInheritedFromCached(const ComputedStyle& other)
     // m_nonInheritedData.m_affectedByDrag
     // m_nonInheritedData.m_isLink
 
+    // Any properties that are inherited on a style are also inherited on elements
+    // that share this style.
+    m_nonInheritedData.m_isPointerEventsInherited = other.m_nonInheritedData.m_isPointerEventsInherited;
+    m_nonInheritedData.m_isVisibilityInherited = other.m_nonInheritedData.m_isVisibilityInherited;
+
     if (m_svgStyle != other.m_svgStyle)
         m_svgStyle.access()->copyNonInheritedFromCached(other.m_svgStyle.get());
     DCHECK_EQ(zoom(), initialZoom());
@@ -441,7 +464,18 @@ void ComputedStyle::removeCachedPseudoStyle(PseudoId pid)
 
 bool ComputedStyle::inheritedEqual(const ComputedStyle& other) const
 {
-    return m_inheritedData == other.m_inheritedData
+    return independentInheritedEqual(other)
+        && nonIndependentInheritedEqual(other);
+}
+
+bool ComputedStyle::independentInheritedEqual(const ComputedStyle& other) const
+{
+    return m_inheritedData.compareEqualIndependent(other.m_inheritedData);
+}
+
+bool ComputedStyle::nonIndependentInheritedEqual(const ComputedStyle& other) const
+{
+    return m_inheritedData.compareEqualNonIndependent(other.m_inheritedData)
         && m_styleInheritedData == other.m_styleInheritedData
         && m_svgStyle->inheritedEqual(*other.m_svgStyle)
         && m_rareInheritedData == other.m_rareInheritedData;